The goal of this project is to characterize and understand how spatially auditory perception is altered by past experience. Experiments will test the hypothesis that spatial auditory processing is hierarchical, and and that experience influences spatial perception through different mechanisms at different processing stages. Specifically, experiments will test whether 1) stimulus-driven excitation and inhibition interact dynamically in low-level processing, explaining the influence of a preceding stimulus (or stimuli) on a subsequent stimulus, whereas 2) top-down training (through both explicit feedback and implicit learning) alters higher-level processing over minutes or hours, changing how spatial precepts are mapped to perceived locations in exocentric space. These hypothesis will be addressed through behavioral experiments that measure how spatial localization accuracy and variability depend on past experience over a range of time scales and experimental paradigms, acoustic measurements that characterize the way in which spatial acoustic cues vary in different acoustical environments, and theoretical models that explore that explore what processing structures could explain empirical results. This work is critical for identifying how the normal human listener adapts and calibrates spatial perception in everyday settings in order to maintain accurate spatial perception in chanbging acoustic environments. By studying dynamic perceptual phenomena that are thought to arise from both bottom-up and top-down processing effects ( and across a range of time scales, from frations of seconds to minutes or hours), this project will provide a coherent picture of how different perceptual phenomena relate and interact. Ultimately, this work will help to elucidate how past experience influences spatial auditory processing, changes spatial auditory resolution and localization accuracy.